{"id":"CVE-2021-47491","state":"PUBLISHED","title":"mm: khugepaged: skip huge page collapse for special files","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: khugepaged: skip huge page collapse for special files\n\nThe read-only THP for filesystems will collapse THP for files opened\nreadonly and mapped with VM_EXEC.  The intended usecase is to avoid TLB\nmisses for large text segments.  But it doesn't restrict the file types\nso a THP could be collapsed for a non-regular file, for example, block\ndevice, if it is opened readonly and mapped with EXEC permission.  This\nmay cause bugs, like [1] and [2].\n\nThis is definitely not the intended usecase, so just collapse THP for\nregular files in order to close the attack surface.\n\n[shy828301@gmail.com: fix vm_file check [3]]","publishedAt":"2024-05-22T08:19:40.101Z","updatedAt":"2026-05-11T13:55:40.703Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0","status":"affected","lessThan":"6d67b2a73b8e3a079c355bab3c1aef7d85a044b8","versionType":"git"},{"version":"99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0","status":"affected","lessThan":"5fcb6fce74ffa614d964667110cf1a516c48c6d9","versionType":"git"},{"version":"99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0","status":"affected","lessThan":"a4aeaa06d45e90f9b279f0b09de84bd00006e733","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/khugepaged.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.4","versionType":"semver"},{"version":"5.10.78","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.14.16","status":"unaffected","lessThanOrEqual":"5.14.*","versionType":"semver"},{"version":"5.15","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/khugepaged.c"]}],"references":["https://git.kernel.org/stable/c/6d67b2a73b8e3a079c355bab3c1aef7d85a044b8","https://git.kernel.org/stable/c/5fcb6fce74ffa614d964667110cf1a516c48c6d9","https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733"],"weaknesses":[],"ingestedAt":"2026-10-29T19:49:19.404Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/47xxx/CVE-2021-47491.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47491","state":"PUBLISHED","datePublished":"2024-05-22T08:19:40.101Z","dateUpdated":"2026-05-11T13:55:40.703Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-05-22T06:20:56.201Z"},"containers":{"cna":{"title":"mm: khugepaged: skip huge page collapse for special files","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: khugepaged: skip huge page collapse for special files\n\nThe read-only THP for filesystems will collapse THP for files opened\nreadonly and mapped with VM_EXEC.  The intended usecase is to avoid TLB\nmisses for large text segments.  But it doesn't restrict the file types\nso a THP could be collapsed for a non-regular file, for example, block\ndevice, if it is opened readonly and mapped with EXEC permission.  This\nmay cause bugs, like [1] and [2].\n\nThis is definitely not the intended usecase, so just collapse THP for\nregular files in order to close the attack surface.\n\n[shy828301@gmail.com: fix vm_file check [3]]"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0","status":"affected","lessThan":"6d67b2a73b8e3a079c355bab3c1aef7d85a044b8","versionType":"git"},{"version":"99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0","status":"affected","lessThan":"5fcb6fce74ffa614d964667110cf1a516c48c6d9","versionType":"git"},{"version":"99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0","status":"affected","lessThan":"a4aeaa06d45e90f9b279f0b09de84bd00006e733","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/khugepaged.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.4","versionType":"semver"},{"version":"5.10.78","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.14.16","status":"unaffected","lessThanOrEqual":"5.14.*","versionType":"semver"},{"version":"5.15","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/khugepaged.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6d67b2a73b8e3a079c355bab3c1aef7d85a044b8"},{"url":"https://git.kernel.org/stable/c/5fcb6fce74ffa614d964667110cf1a516c48c6d9"},{"url":"https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T13:55:40.703Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.10.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.14.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.15"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2021-47491","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-05-22T18:42:55.199651Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-06-04T17:13:59.526Z"}},{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/6d67b2a73b8e3a079c355bab3c1aef7d85a044b8","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/5fcb6fce74ffa614d964667110cf1a516c48c6d9","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/a4aeaa06d45e90f9b279f0b09de84bd00006e733","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-04T05:39:59.599Z"}}]}}}